Laserfiche WebLink
DRAFT <br /> of the vadose zone above the capillary zone; and (3) a cracked concrete building <br /> foundation. For soil sources, the VF development considered resistance from the soil <br /> ' layer only using the same equations,by assuming that the capillary zone was not present <br /> (thickness is equal to 0). <br /> VFs were developed for all organic compounds detected in site soil or groundwater <br /> samples that met EPA criteria for identifying chemicals as VOCs, specifically, those with <br /> a molecular weight of less than 200 grams per mole and a Henry's Law constant of 1 x <br /> 10-5 atmosphere-cubic meters per mole or higher(EPA 1996). <br /> 1 The volatilization factors were developed using the following equations: <br /> H Dw�-cw <br /> VF _ ER x LB x10,L (1-1) <br /> wesp eR m3 <br /> 1+ Dws�cw <br /> ERxLB <br /> where: <br /> Vfwesp = Volatilization factor for groundwater into enclosed-space air <br /> (mg/m3-air per mg/L-water <br /> D w5 = Effective diffusion coefficient for soil between groundwater and <br /> soil surface (cmZ/sec) <br /> Lcw = Depth to groundwater=heap + H, (cm), site-specific <br /> ER = Enclosed-space air exchange rate (L/s), ASTM E 1739-95 <br /> LB = Enclosed-space volume/infiltration area ratio (cm), ASTM E <br /> 1 1739-95 <br /> 1 SOMA 99-2218 6 12/10/99 <br />